(a) Field of the Invention
The present invention relates to a manufacturing method of a flexible display device. More particularly, the present invention relates to a manufacturing method of a display panel for a flexible display device including a plastic substrate.
(b) Description of the Related Art
A liquid crystal display and an organic light emitting diode (OLED) display are representative of flat panel displays that are used widely at present.
The liquid crystal display generally includes an upper panel in which elements such as a common electrode and color filters are formed; a lower panel in which thin film transistors and pixel electrodes are formed; and a liquid crystal layer that is interposed between the two display panels. If a potential difference between a pixel electrode and the common electrode is generated, an electric field is generated in the liquid crystal layer. This electric field determines an orientation, or arrangement direction, of liquid crystal molecules in the liquid crystal layer, with the transmittance of incidence light being determined by the arrangement direction of the liquid crystal molecules. Accordingly, a desired image can be displayed by adjusting the potential difference between the two electrodes.
An OLED display includes a hole injection electrode (anode), an electron injection electrode (cathode), and an organic emission layer formed therebetween. An OLED display is a self-emissive display that emits light in an organic emission layer, through recombination of holes injected from the anode and electrons injected from the cathode.
Such display devices have limited portability and screen size, because they typically use a heavy, fragile glass substrate. Therefore, a display device using a lightweight, impact resistant, and flexible plastic substrate has been developed. However, when a high temperature is applied to such plastic, the plastic has a property of bending or expanding. Accordingly, it is difficult to form a thin film pattern such as an electrode or a signal line on the plastic, and it is desirable to provide a method of manufacturing a display panel using lower temperatures.